I put that same kit on a 1976 20' Coachmen motorhome that was sagging in the rear. Seemed to do that job well but you had to manually monitor the air pressure.
The Coachmen motorhome is long gone and I now have a 1974 20' Argosy motorhome that is in need of something similar. What I've been thinking about doing is adding this same kit only with the addition of leveling valves (one per side) and installing an air compressor and tank (salvaged from our parts 345 motor home).
I can't think of any reason why this wouldn't work.
Air forums # 1674
1974 20' Argosy Motor Home
1974 31' Excella trailer (parting out, as of 4/1/2015 I have wheels, brake drums, windows & holding tanks left to sell)